Upper North Platte River Basin (8)
January 2000

Snow
The snow courses above Seminoe Reservoir have about 65 percent of average snow water equivalent (SWE) recorded for this time of the year (91 percent of last year). SWE in the drainage area above Northgate is about 101 percent of average and 68 percent of last year at this time. SWE in the Encampment River drainage is about 54 percent of normal and 86 percent of last year. Brush Creek SWE for the year is about 96 percent of normal and 101 percent of last year's SWE. Medicine Bow and Rock Creek drainage SWE is about 53 percent of average and 73 percent of last year at this time. For more information see Basin Summary of Snow Courses at the beginning of this report.

Precipitation
Eight reporting stations indicate December precipitation was 89 percent of average and about 146 percent of last year's amount. December precipitation varied from 26 at Rawlins to 127 percent of average at North French Creek SNOTEL. Total water-year-to-date precipitation is about 62 percent of average for the basin, which is about 55 percent of last year's amount. Year to date percentage ranges from 47 to 84 for the 8 reporting stations.

Reservoirs
Seminoe Reservoir is currently storing about 156 percent of normal for this time of the year. Currently, the reservoir is storing 112 percent of last year's amount. Currently, Seminoe Reservoir storage is estimated to be storing 845,600 acre-feet (83 percent of capacity). Last year, at this time, the reservoir had 756,700 acre-feet in storage.

Streamflow
All the following yields are based on the fifty percent chance April through September yield. Yield for the North Platte River near Northgate is expected to be about 156,000 acre-feet (58 percent of average). Encampment River near Encampment is estimated to yield 63,000 acre-feet (40 percent of normal). North Platte River near Sinclair will yield about 358,000 acre-feet (50 percent of normal). Rock Creek near Arlington is estimated to yield 44,000 acre-feet (79 percent of average). Medicine Bow River above Seminoe Reservoir is expected to yield about 57,000 acre-feet (45 percent of normal). Seminoe Reservoir inflow should be about (423,000 acre-feet (50 percent of normal). See the following table for more detailed information on projected runoff.

==================================================================================================================================
                                                  UPPER NORTH PLATTE RIVER BASIN
                                               Streamflow Forecasts - January 1, 2000
==================================================================================================================================
                                              |  <<====== Drier ======  Future Conditions  =======  Wetter =====>>  |             
                                              |                                                                     |
  Forecast Point                     Forecast |  ==================== Chance Of Exceeding * ======================  |
                                      Period  |    90%       70%    |  50% (Most Probable)  |      30%       10%    |  30-Yr Avg.
                                              | (1000AF)  (1000AF)  |   (1000AF)  (% AVG.)  |    (1000AF)  (1000AF) |    (1000AF)
====================================================================|=======================|=====================================
North Platte River nr Northgate      APR-SEP      10.0        97    |      156        58    |       215       302            271
                                                                    |                       |
Encampment River nr Encampment       APR-SEP        23        34    |       63        40    |        92       135            156
                                                                    |                       |
North Platte River nr Sinclair       APR-SEP       137       205    |      358        50    |       511       735            719
                                                                    |                       |
Rock Creek nr Arlington              APR-SEP        26        36    |       44        79    |        53        67             56
                                                                    |                       |
Medicine Bow River ab Seminoe Reserv APR-SEP      12.0        35    |       57        45    |        85       136            127
                                                                    |                       |
Seminoe Reservoir inflow             APR-JUL       150       215    |      382        49    |       549       795            788
                                     APR-SEP       162       243    |      423        50    |       603       868            851
                                                                    |                       |
==================================================================================================================================
                     UPPER NORTH PLATTE RIVER BASIN                     |             UPPER NORTH PLATTE RIVER BASIN
             Reservoir Storage (1000 AF) - End of December              |        Watershed Snowpack Analysis - January 1, 2000
==================================================================================================================================
                                      Usable |  *** Usable Storage ***  |                            Number     This Year as % of
Reservoir                            Capacity|  This      Last          |   Watershed                  of       =================
                                             |  Year      Year     Avg  |                          Data Sites   Last Yr   Average
========================================================================|=========================================================
SEMINOE                               1016.7    845.6    756.7    542.0 |   N PLATTE above Northgate    5       101        68
                                                                        |
                                                                        |   ENCAMPMENT RIVER            3        86        54
                                                                        |
                                                                        |   BRUSH CREEK                 2       101        96
                                                                        |
                                                                        |   MEDICINE BOW & ROCK CREEK   2        73        53
                                                                        |
                                                                        |   N PLATTE above Seminoe     13        91        65
                                                                        |
==================================================================================================================================
 * 90%, 70%, 30%, and 10% chances of exceeding are the probabilities that the actual volume will exceed the volumes in the 
table.

The average is computed for the 1961-1990 base period.

(1) - The values listed under the 10% and 90% Chance of Exceeding are actually 5% and 95% exceedance levels.                  
(2) - The value is natural volume - actual volume may be affected by upstream water management.
(3) - Forecasts produced in cooperation with Alberta Forecasting Staff Canada


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